1. Field of the Invention
The present invention relates to a fryer, and more specifically to a fryer comprising a fry vessel containing water and oil therein and having an oil layer formed on a water layer due to a difference therebetween in specific gravity, and heating pipes, provided in the fryer vessel, for heating the oil layer, and cooling pipes, provided at a lower portion the fryer vessel than the heating pipes, for cooling the oil layer at the lower portion of the fryer vessel.
2. Description of Related Art
Fryers having an oil layer and a water layer are widely known from, for example, Publication of Examined Japanese Patent Application No. 55-40249. In the conventional fryer of the above-mentioned kind, water and oil are contained in a fry vessel, thereby forming a water layer and an oil layer, and a boundary surface therebetween is positioned at a slightly lower portion of the cooling pipes. Then, heating air heated by combustion gas and the combustion gas are passed through the heating pipes as heating fluid so that the oil layer of the fry vessel is heated. Then, air is passed through the cooling pipes as cooling fluid so that the lower portion of the oil layer is cooled. This restrains an acceleration of oxidation of the oil layer caused by an increase in temperature of the entire oil layer. At the same time, this prevents the temperature of the water layer of the fry vessel from being increased. Also, fry sediment and carbide deposited out of the heated oil layer are precipitated in the water layer so that they are prohibited from floating into the oil layer. This prevents deterioration of the oil layer caused by the fry sediment and carbide and generation of oil smoke caused by the carbide. For this reason, the necessity of an oil filtering process is eliminated, and an oil exchange cycle exists so that an amount of waste oil is lessened.
In the conventional fryer of the above-mentioned kind, however, the amount of the fry sediment and that of carbide, which are generated from fried food and precipitated in the water layer, are increased with an increase in the amount of the fried food. As a result, the boundary surface between the water layer and the oil layer rises. When the boundary surface comes close to the heating pipes, temperature of the water layer rises. As a result, there is an increased danger that steam explosion may occur on the boundary surface and heated oil may be scattered. In order to avoid such a danger, the user must carry out drainage to discharge the fry sediment and carbide from the water layer through a drain valve provided at the lower end of the fry vessel. For this reason, the user has to be conversant with the timing of when drainage should be carried out.